Medical Neuroscience explores the functional organization and neurophysiology of the human central nervous system, while providing a neurobiological framework for understanding human behavior. In this course, you will discover the organization of the neural systems in the brain and spinal cord that mediate sensation, motivate bodily action, and integrate sensorimotor signals with memory, emotion and related faculties of cognition. The overall goal of this course is to provide the foundation for understanding the impairments of sensation, action and cognition that accompany injury, disease or dysfunction in the central nervous system. The course will build upon knowledge acquired through prior studies of cell and molecular biology, general physiology and human anatomy, as we focus primarily on the central nervous system.
This online course is designed to include all of the core concepts in neurophysiology and clinical neuroanatomy that would be presented in most first-year neuroscience courses in schools of medicine. However, there are some topics (e.g., biological psychiatry) and several learning experiences (e.g., hands-on brain dissection) that we provide in the corresponding course offered in the Duke University School of Medicine on campus that we are not attempting to reproduce in Medical Neuroscience online. Nevertheless, our aim is to faithfully present in scope and rigor a medical school caliber course experience.
This course comprises six units of content organized into 12 weeks, with an additional week for a comprehensive final exam:
- Unit 1 Neuroanatomy (weeks 1-2). This unit covers the surface anatomy of the human brain, its internal structure, and the overall organization of sensory and motor systems in the brainstem and spinal cord.
- Unit 2 Neural signaling (weeks 3-4). This unit addresses the fundamental mechanisms of neuronal excitability, signal generation and propagation, synaptic transmission, post synaptic mechanisms of signal integration, and neural plasticity.
- Unit 3 Sensory systems (weeks 5-7). Here, you will learn the overall organization and function of the sensory systems that contribute to our sense of self relative to the world around us: somatic sensory systems, proprioception, vision, audition, and balance senses.
- Unit 4 Motor systems (weeks 8-9). In this unit, we will examine the organization and function of the brain and spinal mechanisms that govern bodily movement.
- Unit 5 Brain Development (week 10). Next, we turn our attention to the neurobiological mechanisms for building the nervous system in embryonic development and in early postnatal life; we will also consider how the brain changes across the lifespan.
- Unit 6 Cognition (weeks 11-12). The course concludes with a survey of the association systems of the cerebral hemispheres, with an emphasis on cortical networks that integrate perception, memory and emotion in organizing behavior and planning for the future; we will also consider brain systems for maintaining homeostasis and regulating brain state.

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Sensory Systems: General Principles and Somatic Sensation

We have reached a significant juncture in Medical Neuroscience as we turn our attention to the organization and function of the sensory systems. We will begin our studies with the somatic sensory systems, which includes subsystems for mechanical sensation and pain/temperature sensation. But before we get there, it is worth considering first some organizing principles that will set the stage for studies of somatic sensation and all the other sensory systems of the body.

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Leonard E. White, Ph.D.

Associate ProfessorDepartment of Neurology, Department of Neurobiology, Duke University School of Medicine; Department of Psychology & Neuroscience, Trinity College of Arts & Sciences; Director of Education, Duke Institute for Brain Sciences; Duke University

Hi everyone. Welcome to this tutorial on the general

principles of sensory systems. We are at a bit of a pivot point in the

course where our focus has been on gross brain anatomy.

As well as the principles of neurophysiology that underline neural

signaling and even a discussion of neuroplasticity.

Now we're going to begin to bring these concepts together.

On the one hand, the discussion of anatomy, in the other, the discussion of

cellular physiology and we want to bring them together.

As we discuss the organization and function of our sensory motor systems.

So this is the beginning of that pivot and what I'd like for you to be able to

focus on in this tutorial are some of the general principles that will help us

understand the organization of our sensory systems which is what we'll

discuss first and then we'll move on and discuss the motor systems.

So this topic pertains once again to our key concept or foundational core concept

in the field of neuroscience pertaining to the complexity of the brain.

And this tutorial I trust will help break down some of that complexity for you as

we consider how sensory systems are organized, and how they function.

And this will allow us to maybe reflect for just a moment on this incredible

capacity we have to explore our world. Even the world with inside our own brain.

You know, I'm reminded of a student I once had some years ago who I will not

name in case you're out there somewhere but he showed up one day to the lab and

he said, you know I just don't think the brain should be allowed to study itself.

And I thought, what a profound observation you know, the kidney doesn't

get to study itself nor does the liver, but somehow the brain has the credentials

that allow it to study itself. And I think that is an interesting

thought to consider. Well let's move on and consider what we

have to learn from this tutorial today. So I have several learning objectives for

you, I want you to be able to account for the generation of action potentials in

peripheral axons in response to somatic sensory information.

Now, the somatic sensory system will be the first of the sensory systems that we

consider, so I thinks it's useful to see how this general problem of action

potential generation in a sensory system is realized in this one domain of

sensation, that of somatic sensation. I want you to be able to account for

differences in mechanosensory discrimination across the surface of the

body. Again, we're going to take somatic

sensation as our model paradigm, but the basic principles will apply to our other

sensory systems as well. And I want to consider in fairly general

and broad terms, how information is coded in the nervous system.

So, I'd hope that you'd be able to have a discussion of the important factors that

influence information coding. And one very important concept in sensory

physiology is that of the receptive field.

So I want you to have a thorough understanding of what the receptive field

is. And one way to ensure yourself of that is

to have a discussion with someone about it.

Okay, what I'd like to do next is to consider some general organizational

principles that will apply to our consideration of our sensory systems.

And we'll see how they played out specifically in different systems over

the next several tutorials, but today I'd like to keep it fairly general.

So let's begin with one principal, and that is the principle of neuronal

pathways. So let me illustrate for you, in very

simple terms, what I mean by a neuronal pathway.

Let's imagine that there's some kind of sensory surface out here perhaps this is

the skin. And the skin is innervated by nerve

fibers and those nerve fibers are grown by cells in this case cells that reside

in the dorsal root ganglion so an axon extends out and there's some kind of

specialized receptor structure as the axons reaches the skin surface.

So this is what we call the peripheral axon of this neuron.

So this neuron can be considered a first order neuron in this pathway.

Well there is a central process that enters the nervous system.

So let's say this is now into the central nervous system.

And that first order neuron synapses on a second order neuron.

And that second order neuron projects some distance through the central nervous

system.to typically a third neuron. We'll call that a third order neuron.

And then, that third order neuron provides input to a vast network of

interconnected cells. And some processing station within the

brain, perhaps this processing station is the cerebral cortex.

So, we might have some, some complicated network that allows all this to function.

So we might call this now the cortex. So the neural pathway would be the first

order neuron, the second order neuron, the third order neuron and then once we

get into our complex network that is being modulating by this ascending input,

we sort of give up on our numbering scheme.

So, we'll see how that works? But the pathway, in essence, is a series

of neurons that are connected. But the pathway is essentially a set of

neurons that are connected in a serial fashion.

And this allows neurosignals to be generated at some receptor surface and

then be transmitted into the nervous system ultimately to be processed at the

level of the cerebral cortex. Now, I drew this pathway in the

horizontal dimension across the screen just to make use of the space that I

have, but I want to make an important point about how we talk about our

pathways in the brain. So, let me clear that and redraw this in

the vertical dimension. So often we have some receptor connected

to our first order neuron, which projects to a second order neuron.

But now we often think about this as ascending into the nervous system and